Numerical and experimental study of hot pressing technique for resin-based friction composites

This paper carries out an experimental study to enhance the quality of the characteristic transmittance curve in the infrared range of 2.5–7 µm of the optical magnesium fluoride (MgF2) ceramic. This work evaluates the effectiveness of using vacuum environment in the MgF2 ceramic hot-pressing technique by comparing the density and the quality of the transmittance characteristic curve of two types of specimens manufactured by the hot-pressing technique corresponding to open air and vacuum environment under the same technological parameters including temperature 650°C, time 30 min, and pressure 200 MPa. The results present that, in comparison with using the hot-pressing technique in the open air, when using the hot-pressing technique in a vacuum environment, the transmittance increases about 4–10%, the characteristic transmittance curve is smoother and has fewer peak points, and the wide of peak points are smaller. When hot-pressing in a vacuum environment, the temperature can be up to 750°C in order to obtain the magnesium fluoride (MgF2) ceramic with the highest quality of characteristic line in the infrared range of 2.5–7 µm. Seventeen specimens are manufactured to conduct the experimental study in order to figure out the optimal set of technological parameters (temperature T = 640.9°C, time t = 33.0 min, and pressure P=231.4 MPa) when hot-pressing in a vacuum environment by the experimental planning approach.

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Comparison Experimental Study on Apparent Porosity of Brake Linings for Car Based on Water Granulating Technology

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.773.259 ◽

2013 ◽

Vol 773 ◽

pp. 259-262

Author(s):

Zhen Yu Wang ◽

Tie Shan Wang ◽

Li Song

Keyword(s):

Experimental Study ◽

Natural Frequency ◽

Hot Pressing ◽

Production Efficiency ◽

Apparent Porosity ◽

Cavity Volume ◽

Pressing Time ◽

Pressing Process

In this paper, the contrast test has been done on the brake linings that have been made by water granulating technology. As a result, by contrast with the brake linings that have been done at the same material and producing technology, it was preliminary demonstrated that the apparent porosity of the brake linings that have been made by the granulating technology could be enhanced greatly, so on the hot-pressing process, products exhausting has been easy, the die cavity volume could be decreased, the hot-pressing time could been shorten, the production efficiency could be enhanced, the natural frequency of the braking lining could be reduced, the possibility of the braking noise could be decreased.

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Wear of Metal-Bonded Diamond Tools in Different Abrasive Processes

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.291-292.85 ◽

2005 ◽

Vol 291-292 ◽

pp. 85-90 ◽

Cited By ~ 2

Author(s):

Xi Peng Xu ◽

Q.L. Han ◽

Yuan Li

Keyword(s):

Experimental Study ◽

Silicon Carbide ◽

Hot Pressing ◽

Surface Grinding ◽

Vertical Force ◽

Diamond Tools ◽

Circular Sawing ◽

Refractory Bricks

In this present work, an experimental study was carried out to investigate the wear of metal-bonded diamond tools (specimens) in five abrasive processes – stirring diamond specimens in rock slurries and surface grinding the specimens with a vitrified alumina wheel as well as circular sawing of refractory bricks, vitrified silicon carbide wheels and natural granite with segmented diamond blades. Three diamond specimens of different hardness were fabricated by hot pressing. In addition to following the worn morphologies of the diamond tools, forces and power were also monitored in four abrasive processes. During stirring and surface grinding, the wear of the diamond specimens decreased with increasing specimen hardness, whereas the vertical force in surface grinding increased with the specimen hardness. In sawing of granite, however, the wear of the blades was closely related to the vertical force generated in sawing rather than the hardness of the diamond segments. The trends of force changes in sawing of refractory bricks were comparable to those in sawing of granite. But the force ratios in sawing of the SiC wheel were found to be much higher than those in sawing of other two materials.

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Experimental study on the restoration from a tilt-azimuth series for improvement in resolution

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010013955x ◽

1995 ◽

Vol 53 ◽

pp. 636-637

Author(s):

Norio Baba ◽

Norihiko Ichise ◽

Syunya Watanabe

Keyword(s):

Experimental Study ◽

Spherical Aberration ◽

Incident Beam ◽

Optical Parameters ◽

Beam Tilting ◽

Illumination Method ◽

Restoration Method ◽

Illumination Mode

The tilted beam illumination method is used to improve the resolution comparing with the axial illumination mode. Using this advantage, a restoration method of several tilted beam images covering the full azimuthal range was proposed by Saxton, and experimentally examined. To make this technique more reliable it seems that some practical problems still remain. In this report the restoration was attempted and the problems were considered. In our study, four problems were pointed out for the experiment of the restoration. (1) Accurate beam tilt adjustment to fit the incident beam to the coma-free axis for the symmetrical beam tilting over the full azimuthal range. (2) Accurate measurements of the optical parameters which are necessary to design the restoration filter. Even if the spherical aberration coefficient Cs is known with accuracy and the axial astigmatism is sufficiently compensated, at least the defocus value must be measured. (3) Accurate alignment of the tilt-azimuth series images.

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Microstructure of mechanically alloyed and hot-pressed Al5CuZr2

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100177982 ◽

1990 ◽

Vol 48 (4) ◽

pp. 970-971

Author(s):

T. E. Mitchell ◽

P. B. Desch ◽

R. B. Schwarz

Keyword(s):

Mechanical Alloying ◽

Vickers Hardness ◽

Hot Pressing ◽

Rapid Quenching ◽

Hardened Steel ◽

Alloyed Powder ◽

Ion Milling ◽

Mechanical Grinding ◽

Mechanically Alloyed ◽

Steel Container

Al3Zr has the highest melting temperature (1580°C) among the tri-aluminide intermetal1ics. When prepared by casting, Al3Zr forms in the tetragonal DO23 structure but by rapid quenching or by mechanical alloying (MA) it can also be prepared in the metastable cubic L12 structure. The L12 structure can be stabilized to at least 1300°C by the addition of copper and other elements. We report a TEM study of the microstructure of bulk Al5CuZr2 prepared by hot pressing mechanically alloyed powder.MA was performed in a Spex 800 mixer using a hardened steel container and balls and adding hexane as a surfactant. Between 1.4 and 2.4 wt.% of the hexane decomposed during MA and was incorporated into the alloy. The mechanically alloyed powders were degassed in vacuum at 900°C. They were compacted in a ram press at 900°C into fully dense samples having Vickers hardness of 1025. TEM specimens were prepared by mechanical grinding followed by ion milling at 120 K. TEM was performed on a Philips CM30 at 300kV.

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